With the recent interest in Erlang and generally everything that promises to help with making concurrent programming easier, a lot of unfamiliar terms have popped up. As always in Computer Science, none of these technologies are new.

The idea behind Actors has been around for decades, but has recently been pushed into the public eye by Erlang which makes Actor-style programming easy. Erlang does so with lightweight processes, terse syntax for sending messages to processes, and the use of pattern matching to process incoming messages. A new library for Ruby 1.9 called Revactor adds very Erlang-style Actors to Ruby.

Coroutines have also been around for a very long time, and in many languages in various shapes. Starting out as concurrency primitives in the 60's, they disappeared from the public eye when preemptively scheduled threads became popular. Some languages, however, have retained them. Python has had the Generator feature, a special kind of Coroutine for some time. Lua has had full Coroutines as well. Languages like C also had libraries for Coroutines such as libtask or Protothreads. Ruby 1.9 has added a feature called Fibers, both usable as full or Generator-like Coroutines.

We talked to MenTaLguY, a longtime Ruby community member working on various areas of Concurrency. The interview tries to put Actors, Coroutines in perspective and also see how these related to the work going on in Rubinius, which also brings its own set of concurrency primitives such as Channels to communicate between threads.

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Thanks for the link to my interview with Tony. Another resource that's worth noting is probably my article on Actors in Ruby, which includes some input from Tony and MenTaLguY, along with Joe Armstrong and others.